<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .box {
      height: 900px;
      background-color: rgb(57, 182, 63);
      /* float: ; */
    }

    .fff {
      float: right;
    }

    .b {
      float: left;
      width: 200px;
      height: 200px;
    }

    .box1 {
      /* flex: 1; */
      background-color: rgb(228, 28, 28);
    }

    .box2 {
      /* flex: 2; */
      background-color: rgb(28, 88, 228);
    }

    .box3 {
      /* flex: 3; */
      background-color: rgb(211, 33, 137);
    }
  </style>
</head>

<body>
  <div class="box">
    <div class="fff">
      <div class="b box1">1</div>
      <div class="b box2">2</div>
      <div class="b box3">3</div>
    </div>
  </div>
</body>

</html>